A conventional Hall thruster propulsion system includes, inter alia, a thruster assembly, including magnetic field source(s), a cathode assembly including an emitter, a heater, and a keeper, a propellant storage and delivery system, and a power processing unit (PPU) to power the plasma discharge circuit and to selectively distribute power to the various system components.
Prior PPUs of Hall thrusters typically include separate power supplies for the keeper, the heater, the magnetic source, and the plasma discharge circuit. Typically, the PPU has the largest volume and largest mass of all components in the Hall thruster system. Reducing the size of the PPU by combining and/or eliminating one or more of the various power supplies for the keeper ignition, the heater, the magnetic source, or plasma discharge circuit is one way to reduce the overall size and weight of the Hall thruster system.
One attempt to overcome the problems associated with the separate power supplies of the PPU is disclosed in U.S. Pat. No. 6,031,334 entitled “Method And Apparatus For Selectively Distributing Power In A Thruster System”, incorporated by reference herein. The '334 patent discloses a PPU which includes power supply coupled to a power distribution circuit which selectively provides power to the heater, keeper, and magnetic field source. The power distribution circuit is specifically located between the power supply and the heater, the keeper, and magnetic field source. This design of the distribution circuit does not supply power to the plasma discharge, hence the '334 method and apparatus as disclosed in the '334 patent requires a separate power supply for the plasma discharge, as well as complicated electronics associated with the distribution circuit, which both add mass and volume to the Hall thruster system.